what is annealing?

Question

it is a heat treatment process

Answer 1

Annealing may refer to:

Annealing (metallurgy), a heat treatment that alters the micro structure of a material causing changes in properties such as strength and hardness
Annealing (glass), heating a piece of glass to remove stress
Annealing (biology), DNA or RNA pairing by hydrogen bonds to a complementary sequence, forming a double-stranded polynucleotide
Simulated annealing, a technique for searching for a solution in a space otherwise too large for "ordinary" search methods to yield results


http://en.wikipedia.org/wiki/Annealing

Answer 2

Annealing, in metallurgy and materials science, is a heat treatment where in the microstructure of a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces equilibrium conditions by heating and maintaining at a suitable temperature, and then cooling very slowly. It is used to induce softness, relieve internal stresses, refine the structure and improve cold working properties. There are several phases in the annealing process, with the first being the recovery phase, which results in softening of the metal through removal of crystal defects and the internal stresses which they cause. The second phase is recrystallization, where new grains nucleate and grow to replace those deformed by internal stresses. If annealing is allowed to continue once recrystallization has been completed, grain growth will occur, in which the microstructure starts to coarsen and may cause the metal to have less than satisfactory mechanical properties.

In the semiconductor industry, silicon wafers are annealed, so that dopant atoms, usually boron, phosphorus or arsenic, can be incorporated into substitutional positions in the crystal lattice, resulting in drastic changes in the electrical properties of the semiconducting material.

In the cases of copper, steel, and brass this process is performed by substantially heating the material (generally until glowing) for an extended period of time and allowing it to cool slowly. In this fashion the metal is softened and prepared for further work such as shaping, stamping, or forming.

Annealing, in glassblowing and lampworking, is the process of heating, and then slowly cooling glass to increase "softness" (ductility) and durability. This process relieves the internal stresses, making the glass much more durable. Glass which has not been annealed will crack or even shatter when subjected to a relatively small temperature change or other shock.

Glass is heated until the temperature reaches a stress-relief point, that is, the "annealing temperature" at which the glass is still too hard to deform, but is soft enough for the crystal structure of the material to flow together. The piece is then allowed to heat-soak until its temperature is even throughout. The time necessary for this varies depending on the type of glass and thickness of the thickest section.

The glass is then slowly cooled at a predetermined rate until its temperature is below a critical point when the internal stresses are balanced with the surface tension on the face of the glass. Then the temperature can safely be dropped to room temperature. After the annealing process the material can be cut to size, drilled or polished.

In mathematics and applications, quantum annealing is a method for finding solutions to combinatorial optimization problems and ground states of glassy systems using quantum fluctuations.

Unlike simulated annealing, which employs the strategy of slow cooling (physically, or in simulation) to find the ground state of glassy systems (physical glass with a rugged potential energy landscape or a mathematical objective function with many local minima), Quantum annealing is basically annealing of glassy systems down to their global minimum (at least to a good approximation) using quantum fluctuations instead of thermal ones.

Answer 3

Annealing may refer to:

Annealing (metallurgy), a heat treatment that alters the micro structure of a material causing changes in properties such as strength and hardness
Annealing (glass), heating a piece of glass to remove stress
Annealing (biology), DNA or RNA pairing by hydrogen bonds to a complementary sequence, forming a double-stranded polynucleotide
Simulated annealing, a technique for searching for a solution in a space otherwise too large for "ordinary" search methods to yield results
Information annealing or knowledge annealing, a network-based information system in which all users of the system are permitted to change the system at will
Quantum annealing, a method for finding solutions to combinatorial optimization problems and ground states of glassy systems using quantum fluctuations

Answer 4

Annealing is a heat treatment used to remove the stresses in a steel component. This treatment softens the steel by the process

Answer 5

Annealing (metallurgy), a heat treatment that alters the micro structure of a material causing changes in properties such as strength and hardness

Answer 6

Certain materials (mostly glass, ceramic, and metal) form different crystalline structure if they cool from their molten state slowly instead of quickly. Annealing controls the rate of cooling of materials so they crystallize with certain desired properties.

A good example: pyrex glass (used to make telescope mirrors), when cooled quickly, will have an uneven crystalline structure that produces uneven stresses across the surface of the material. If you use such pyrex to make a telescope mirror, the mirror won't hold the fine figure required for an accurate focusing of light. By annealing the pyrex (cooling it slowly through the gradual reduction of the heat applied), it crystallizes in nice even lattices, there are no stress areas, and the material will hold its figure much better across a wide temperature range.

Answer 7

Annealing is drawing the temper or hardness out of a metal. This is done by heating the metal red to white hot and letting it cool slowly. The faster you cool metal after heating the harder it becomes. If you wont the metal real soft you may heat and slowly cool it more than once.

Answer 8

Annealing is basically a heat treatment process to obtain desired proerties.It is one of the most important heat treatment operations. The consideration of structural stabilization is obtained by first heatin to remove instability and then cooling. The various objectives achieved by annealing are
1. softens the metal to case machinability
2. refines and removes structural inhomogeneity
3. relieves internal stresses
4. removes gases trapped during casting of metals
5. changes physical and mechanical properties

The varoius types of aneealing operations are:

Full aneealing : Heating of steel to about 50-75C above the upper critical temperature for hypoeutectoid steel and by the same same temperature above the lower critical temp for hpereutectoid steel.
Holding it at this temperature for a sufficient time
Slowly cooling it in the furnace.

Process annealing: It is done to remove the effects of cold working and to soften the steel to make it suitable for further plastic deformation. The exact temperature depends upon the extent of cold working, grain size, composition.

Spheroidise annealing: This process causes the agglomeration of all carbides int he steel in the form of small graglobules or spheroids.this process is usually applied to high carbon steels. the process consists of heating the steel slightly above the lower critical point, holding at this temperature and then cooling slowly to a temperature of 600C.

Diffusion annealing: In order to remove the heterogeniety in the composition of heavy castings, this process is used. It homogenises the austenite grain when eated to above the upper critical point. This process is always followed by full annealing of fine-grained structure int he castings.

Answer 9

What Is Annealing

Answer 10

Annealing refers to slowing cooling a material (generally metal), generally to obtain its softest state. Normally, hot metal is either "quenched" by spraying or submerging in water or oil, "normalized" by allowing it to air cool, or "annealed" by slowing the cooling process down even further by leaving it in a furnace where the temperature is gradually reduced.